Cats have become one of the world’s most invasive predators

When thinking about the causes behind species extinctions, invasive species such as rats or snakes and the looming threat of climate change often come to mind. However, an unexpected contender tops the list of culprits: domestic cats.

Although cats may appear as gentle and lovable companions, their impact on ecosystems worldwide reveals a far more destructive side. Beneath their charming exterior lies one of nature’s most efficient predators – stealthy, adaptable, and relentless.

Cats: Predators without boundaries

Whenever a cat moves with silent determination, it’s likely closing in on its next prey. With no specific preferences and an insatiable hunting instinct, both domestic and feral cats have driven the extinction of numerous species, earning the title of one of the most invasive predators on Earth.

According to a study published in Proceedings of the National Academy of Sciences in July 2016, cats have contributed to the extinction of 63 species in modern times. Recent research has further illuminated the staggering breadth of their ecological impact.

A December 2023 study in Nature Communications documented over 2,000 species hunted by cats. 

Among these, 347 species are classified as threatened, near-threatened, or extinct by the International Union for Conservation of Nature (IUCN). Cats show no favoritism when it comes to prey, but birds appear to be their preferred target.

Feral cats are invasive predators

In the United States alone, cats – both domestic and feral – are responsible for the deaths of approximately 2.4 billion birds and 12.3 billion small mammals annually. 

In Australia, feral cats kill over two billion native animals every year, including marsupials, reptiles, and ground-nesting birds.

Of the 2,084 species preyed upon by cats, birds top the list at 981, followed by 463 reptile species. 

Iconic examples of their destructive influence include the Stephens Island wren, driven to extinction by a single housecat named Tibbles, and the now-extinct Hawaiian crow and New Zealand quail. Even today, feral cats remain a top threat to endangered species like the Galápagos petrel.

Unique vulnerability of island ecosystems

Cats wreak havoc in both mainland and island ecosystems, but the damage they cause varies significantly. Islands are especially vulnerable due to the lack of natural predators and the evolution of native species without defenses against invasive hunters.

Ground-nesting birds, slow-moving reptiles, and small mammals are particularly at risk on islands. 

The introduction of cats, apex predators in such environments, has led to dramatic population declines and outright extinctions. Islands house three times more species of conservation concern linked to cats compared to mainland habitats.

On the mainland, the impact of cats is more nuanced. While larger landmasses often support native predators and competitors, cats still exploit fragmented habitats in urban and suburban areas. 

They prey on small mammals and birds in already stressed ecosystems, disrupting food chains and sometimes outcompeting native predators. However, the diversity of competitors and predators on the mainland somewhat mitigates their impact compared to the devastation seen on islands.

Why cats are such effective predators

Cats’ ability to spread and thrive as invasive predators stems from a combination of biological traits and human support:

Rapid reproduction 

A single female cat can produce up to 180 kittens in her lifetime under ideal conditions, allowing feral populations to grow quickly in areas with sufficient food and few predators.

Versatile hunting skills 

Equipped with sharp claws, keen night vision, acute hearing, and razor-sharp teeth, cats are adept at hunting a wide range of prey, including birds, rodents, reptiles, and insects.

Dietary flexibility 

Cats rely solely on animal protein, enabling them to survive on prey alone. Their evolutionary ability to extract water from their meat-based diet allows them to thrive in diverse environments.

Behavioral adaptability 

Cats employ stealth and ambush tactics to outwit prey, showing remarkable patience and persistence in hunting even elusive or cautious species.

Human support 

Unlike other invasive predators, cats benefit directly from humans. Feral cats often rely on food scraps, garbage, or intentional feeding, which shields them from natural selection pressures like starvation. Meanwhile, even well-fed domestic cats hunt for sport, exacerbating their ecological impact.

Managing the invasive cat issue

Efforts to control cat populations, such as trap-neuter-return (TNR) programs, aim to reduce feral cat numbers without removing them entirely. However, cats’ adaptability and widespread presence across all continents except Antarctica mean their ecological impact persists.

Balancing the affection many people feel for cats with the urgent need to protect vulnerable wildlife is an ongoing challenge. 

While cats remain beloved companions to millions, their role as one of the most destructive invasive species highlights the necessity for responsible management. Protecting ecosystems from their predation is not merely a choice – it’s an ecological imperative.

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